New uslot function and usl macro.

* struct.c (struct_init): Register uslot intrinsic function.
(uslot_fun): New static function.
(uslot): New function.

* struct.h (uslot): Declared.

* share/txr/stdlib/struct.tl (usl): New macro.

* lisplib.c (struct_set_entries): Add usl macro.

* txr.1: Documented uslot and usl.

1 files changed, 20 insertions, 0 deletions

diff --git a/struct.c b/struct.c
index 040b43be..acd28f68 100644
--- a/struct.c
+++ b/struct.c
@@ -133,6 +133,7 @@ void struct_init(void)
   reg_fun(intern(lit("struct-type"), user_package), func_n1(struct_type));
   reg_fun(intern(lit("method"), user_package), func_n2(method));
   reg_fun(intern(lit("super-method"), user_package), func_n2(super_method));
+  reg_fun(intern(lit("uslot"), user_package), func_n1(uslot));
   reg_fun(intern(lit("umethod"), user_package), func_n1(umethod));
 }
 
@@ -791,6 +792,25 @@ val super_method(val strct, val slotsym)
   return func_f0v(cons(super_slot, strct), method_fun);
 }
 
+static val uslot_fun(val sym, val strct)
+{
+  val self = lit("uslot");
+  struct struct_inst *si = struct_handle(strct, self);
+
+  if (symbolp(sym)) {
+    loc ptr = lookup_slot(strct, si, sym);
+    if (!nullocp(ptr))
+      return deref(ptr);
+  }
+
+  no_such_slot(self, si->type, sym);
+}
+
+val uslot(val slot)
+{
+  return func_f1(slot, uslot_fun);
+}
+
 static val umethod_fun(val sym, struct args *args)
 {
   val self = lit("umethod");